Anatomy and Physiology for General Nursing & Midwifery (GNM) SM Raju, Bindu Raju, M Sivakumar
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Introduction to the Study of Anatomy and PhysiologyChapter 1

The earliest studies of ‘anatomy and physiology’ were aimed at treating illnesses and injuries. Such studies set the stage for the development of modern medicine with standardized terms.
Anatomy deals with the structure (morphology) of the body and its parts, whereas physiology studies the functions of these parts.
Anatomists rely on observation, while physiologists employ experimentation. The functional role of a part depends on how it is constructed.
The human body begins to take shape during the embryonic development. While the embryo is a tiny hollow ball of dividing cells, it begins forming the tissues and organs that compose human body. By the end of 3rd week of human embryo, it has bilateral symmetry (a body plane in which the left and right sides are the mirror images of each other) and has developing vertebrate characteristics that will support an upright body:
  1. The human body is a precisely structured container of chemical reactions.
  2. Biology is the study of living things that include the study of the human body.
  3. The study of body structure, which includes size, shape, composition and perhaps even coloration is called ‘anatomy’.
  4. The study of how body functions is called ‘physiology’.
The purpose of this chapter is to enable the nursing students to gain an understanding of ‘anatomy and physiology’ with the emphasis on the normal structure and function.
Levels of Structural Organization (Fig. 1.1)
Chemical Level
The chemicals that make up the body may be divided into two major categories. They are inorganic and organic:
  1. Inorganic chemicals are usually simple molecules made of one or more elements other than carbon. For example, water, oxygen, carbon dioxide (an exception) and minerals such as iron, calcium and sodium.
  2. Organic chemicals are often very complex and always contain the elements carbon and hydrogen. Examples are carbohydrates, fats, proteins and nucleic acids.
Cellular Level
The smallest living units with a definite structure and function are cells. Cells are the smallest living subunits of a multicellular organism such as a human being. There are many different types of cells; each is made of chemicals and carries out specific chemical reactions.
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Figure 1.1: Levels of structural organization
Tissue Level
A tissue is a group of cells with similar structure and function. There are four groups of tissue (Figs 1.2A to D):
  1. Epithelial tissue cover or line body surfaces; some are capable of producing secretions with specific functions. The outer layer of skin and sweat glands are examples of epithelial tissue.
  2. Connective tissue connects and supports parts of the body; also some are involved in transport and storage materials. Examples are blood, bone and adipose tissue (fat).
  3. Muscle tissue is specialized for contraction, which brings about movement. Examples are skeletal muscles, smooth muscles and the heart muscle (cardiac muscle).
  4. Nerve tissue is specialized to generate and transmit electrochemical impulses that regulate body functions. The examples are brain and optic nerves.
Organ Level
An organ is a group of two or more different types of tissues precisely arranged to perform specific functions and usually have recognizable shape. The examples are heart, brain, kidneys, liver and lungs.
System Level (Organ Systems)
An organ system is a group of organs that all contribute to a particular function. Examples are the circulatory, respiratory and digestive systems. Each organ system carries out its own specific function, but for the organism to survive, the organ systems must work together; this is called integration of organ system.
Organism Level
Organism level is the most complex level. All the organ systems of the body that function with one another constitute the total organism (one living individual).
Life Processes or Characteristics of Life
All living organisms carry on certain processes that set them apart from non-living things. The following are several of the more important life processes in humans:
  1. Metabolism is the sum of all chemical reactions that occur in the body. The first phase of metabolism is called catabolism that provides energy needed to sustain life by breaking down energy yielding substances such as food molecules. The other phase is called anabolism that uses the energy from catabolism to make various molecules that form body structures and enable them to function.
  2. Assimilation is the changing of absorbed substances into forms that are chemically different from those that entered the body.
  3. Responsiveness is the ability to detect and respond to changes outside or inside the body. Seeking water to quench thirst is a response to water loss from body tissue.
  4. Movement includes motion of the whole body, individual organs, single cells or even structures inside cells.
  5. Growth refers to an increase in size. It may be due to an increase in: the size of existing cells, the number of cells or the amount of substance surrounding cells. It occurs whenever an organism produces new body materials faster than old ones, which are worn out or replaced.
  6. Differentiation is the process whereby unspecialized cells become specialized cells. Specialized cells differ in structure and function from the cells from which they originated.
  7. Reproduction refers either to the formation of new cells for growth, repair or replacement, or to the making of a new individual.
  8. Others include:
    1. Respiration: Obtaining oxygen and eliminating carbon dioxide.
    2. Digestion: Breaking down food substances chemically and mechanically.
    3. Absorption: The passage of substances through certain membranes.
    4. Circulation: The movement of substances within the body in body fluids.
    5. Excretion: Removal of wastes that are produced by body.
Maintenance of Life or Survival Needs
The structures and functions of almost all body parts help to maintain the life of organism. The only exception is an organism’s reproductive structure, which ensure that its species will continue into the future. Life requires certain environmental factors, which includes the following:
  1. Water is the most abundant chemical in the body and it is required for many metabolic processes and provides the environment in which most of them take place. Water also transports substances within the organism and is important in regulating body temperature.
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    Figures 1.2A to D: Structural organization in tissue. A. Connective tissue; B. Simple columnar epithelium; C. Skeletal muscle; D. Neuron cell
  2. Food is the substances that provide the body with necessary chemicals (nutrients) in addition to water. Food is used for energy supply, the raw materials for building new living matter and other help such as to regulate vital chemical reactions.
  3. Oxygen is required to release energy from food substances. This energy in turn drives metabolic processes. Approximately 20% of the air we breathe is oxygen.
  4. Heat (body temperature) is a form of energy; it is the product of metabolic reactions. Normal body temperature is around 37°C or 98°F. Both low and high body temperatures are dangerous to the organism.
  5. Pressure (atmospheric) is necessary for our breathing.
Principal Organ Systems of The Human Body
  1. Integumentary system includes the skin and structures derived from it, such as hair, nails, sweat and sebaceous glands. It protects the body and forms a barrier to pathogens and chemicals. Helps to regulate body temperature, eliminates waste, synthesize vitamin D and receive certain stimuli such as temperature, pressure and pain.
  2. Skeletal system includes all 206 bones of the body, their associated cartilage and the joints of the body. Bones support and protect the body, assist in body movement, store minerals and also house bone marrow that produces blood cells.
  3. Muscular system specifically refers to skeletal muscle tissue and tendons. They participate in bringing about movement, maintaining posture and produces heat.
  4. Circulatory and cardiovascular system includes the heart, blood and blood vessels. It transports oxygen and nutrients to tissues and removes waste.
  5. Lymphatic system is sometimes included with the immune system or circulatory system because it works closely with both systems. The lymph, lymphatic vessels and structures are organs (spleen and lymph 4nodes) containing lymph tissue. It cleans and returns tissue fluid to the blood and destroys pathogens that enter the body.
  6. Nervous system includes the brain, spinal cord, nerves and sense organs such as the eye and ear. Its function is to interpret sensory information, regulate body functions such as movement by means of electrochemical impulses.
  7. Endocrine system includes all hormone producing glands and cells such as the pituitary gland, thyroid gland and pancreas. Hormones regulate body functions.
  8. Respiratory system includes the lungs and a series of associated passageways such as the pharynx (throat), larynx (voice box), trachea (windpipe) and bronchial tubes leading into and out of them. Its function is to exchange oxygen and carbon dioxide between the air and blood.
  9. Digestive system is a long tube called gastrointestinal (GI) tract and associated organs such as the salivary glands, liver, gallbladder and pancreas. It breaks down and absorbs food for use by cells and eliminates solid and other waste.
  10. Urinary and excretory systems include the kidneys, urinary bladder and urethra that together produce, store and eliminate urine. Removes waste products from the blood, and regulate volume and pH of blood.
  11. Immune system consists of several organs, as well as white blood cells in the blood and lymph. It includes the lymph nodes, spleen, lymph vessels, blood vessels, bone marrow and white blood cells (lymphocytes). They provide protection against infection and disease.
  12. Reproductive system includes organs that produce, store and transport reproductive cells (sperms and eggs). In women, provides a site for the developing embryo (fetus).
  • All of the above systems function together to help the human body to maintain homeostasis. A person who is in good health is in a state of homeostasis.
  • Homeostasis reflects the ability of the body to maintain relative stability and to function normally despite constant changes. Changes may be external or internal and the body must respond appropriately.
  • As we continue to study the human body, keep in mind that the proper functioning of each organ and organ system has a role to perform in maintaining homeostasis.
  • The human body uses homeostasis mechanisms to maintain its stable internal environment.
Homeostasis mechanism work much like a thermostat (negative feedback) that is sensitive to temperature and maintains a relative constant water temperature in a water boiler.
To communicate effectively with one another, researchers and clinicians have developed a set of terms to describe anatomy that have precise meaning. Use of these terms assumes the body in the anatomical position (Figs 1.3A and B). This means that the body is standing erect, face forward with upper limbs at the sides and with the palms forward.
As a standard point or frame of reference, the human body is described as being in the anatomical position when it is standing erect, facing you, feet together flat on the floor, the arms slightly raised from the sides with the palms facing forward. Here is a list of useful directional terms. Know not only what they mean but also how to correctly use them.
Anatomical Planes (Fig. 1.4)
  1. Sagittal plane divides the body into right and left halves:
    • Midsagittal divides the body right down the middle into equal halves
    • Parasagittal divides the body into unequal parts.
  2. Coronal (Frontal) plane divides the body into front and back.
  3. Transverse plane divides the body into superior (top) and inferior (bottom) parts.
  4. Supine is lying on the back.
  5. Prone is lying on the abdomen.
Relative Position (Orientation and Directional Terms)
Terms of relative position describe the location of one body part with respect to another (Fig. 1.5). This includes the following:
  1. Superior means that a body part is above another part or is closer to the head.
  2. Inferior means that a body part is below another body part or towards the feet.
  3. Anterior means towards the front.
  4. Ventral also means towards the front.
  5. Posterior is the opposite of anterior; it means towards the back.
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    Figures 1.3A and B: Anatomical position. A. Anterior; B. Posterior
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    Figure 1.4: Anatomical planes
  6. Dorsal also is the opposite of anterior; it means towards the back.
  7. Medial relates to an imaginary midline dividing the body in equal right and left halves, e.g. the nose is medial to the eyes.
  8. Lateral means towards the side with respect to the imaginary midline, e.g. the ears are lateral to the eyes.
  9. Proximal describes a body part that is closer to a point of attachment or closer to the trunk of the body than another part, e.g. the elbow is proximal to the wrist.
  10. Distal is the opposite of proximal. It means that a particular body part is farther from the point of attachment or farther from the trunk of the body than another part, e.g. the fingers are distal to the wrist.
  11. Superficial means situated near the surface.
  12. Peripheral also means outward or near the surface.
  13. Deep describes parts that are more internal.
  14. Cortex the outer layer of an organ.
  15. Medulla the inner portion of an organ.
Terms for Common Movements
  1. Flexion: Bending at a joint to approximate the two connected parts together.
  2. Extension: Straightening out from a position of flexion.
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    Figure 1.5: Orientation and directional terms
  3. Abduction: Drawing away from the median axis of the body.
  4. Adduction: Bringing toward the median line of the body.
The whole body is built around the bony framework and consists of three main parts:
  • The head and neck
  • The trunk that includes chest, abdomen and pelvis
  • Limbs that includes upper and lower limbs.
The skull consists of cranium that protects brain and eyes, and the mandible that is hinged to the skull. The movement of mandible is essential for chewing and speech.
Thorax is the upper part of the trunk, its wall is made of bony framework that houses the lungs and heart apart from the contents of the mediastinum:
  1. Anteriorly the thorax is bounded by sternum, costal cartilage and front ends of the ribs.
  2. Posteriorly it is bounded by dorsal part of the vertebral column made of 12 thoracic vertebral bones and intervertebral disks.
  3. Laterally it is bounded by 12 ribs and intercostal muscles.
  4. Superiorly it is bounded by the root of the neck with its muscles and blood vessels.
  5. Inferiorly it is bounded by the diaphragm, which separates the thorax from the abdomen. Diaphragm is a dome-shaped muscular structure. The esophagus, aorta and inferior vena cava pass through it.
Contents of Thorax
  1. Central part of the thoracic cavity is occupied by the mediastinum that extends anteriorly from behind the sternum to vertebral column posteriorly. On either side of the sternum lungs are situated.
  2. Heart is situated in the left side of the mediastinum enclosed in a fibrous bag called pericardium.
  3. Trachea enters the thorax through its superior opening from the neck and passes down along the posterior aspect of the mediastinum until it divides into left bronchus and right bronchus that enter the two lungs.
  4. Esophagus as continuation of pharynx enters the thorax through its superior opening from the neck. It lies just in front of and to the left of the vertebral column and behind the trachea. It enters the abdomen through an opening in the diaphragm to join the stomach.
  5. Aorta is the continuation of arch of the aorta; the superior and inferior vena cava, the thoracic duct and the lymph nodes are the other contents of the thorax.
Abdominopelvic Cavity
Abdomen is the biggest cavity in the body, which is arbitrarily divided into abdomen proper and pelvis. The pelvis is bounded posteriorly by the sacrum, ischium on either sides, pubic bone in the front and muscles of the pelvic floor inferiorly:
  1. Abdomen is bounded anteriorly by the muscles of the abdominal wall; the rectus, internal and external oblique, and transversus on either side.
  2. It is bounded posteriorly by the lumbar part of the vertebral column, psoas, quadratus lumborum and iliacus muscles.
  3. Superiorly it is bounded by the diaphragm.
  4. Inferiorly the abdominal cavity is continuous with the superior opening of the pelvis. 7
Contents of the Abdominal Cavity
  • Stomach and intestine
  • Liver, gallbladder and spleen
  • The pancreas, kidneys, adrenal glands, abdominal aorta and inferior vena cava. All of these structures lie posterior to the peritoneum.
Contents of the Pelvic Cavity
  • The sigmoid colon, pelvic colon and the rectum
  • The urinary bladder
  • Reproductive organs in the female
  • Some loops of the small intestine.
Body Cavities
  1. Many organs and organ systems in the human body are housed in compartments called body cavities (Fig. 1.6).
  2. These cavities protect delicate internal organs from injuries and from the daily wear of walking, jumping or running.
  3. The body cavities also permit organs such as the lungs, the urinary bladder and the stomach to expand and contract, while remaining securely supported.
  4. The body can be divided into an appendicular portion (upper and lower limbs) and an axial portion (head, neck and trunk), which contains a dorsal and a ventral cavity. Organs within these cavities are called viscera:
    1. The dorsal cavity can be divided into the cranial cavity and vertebral canal.
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      Figure 1.6: Anatomical cavities
    2. The ventral cavity is made up of a thoracic cavity (mediastinum divides the thorax into right and left halves) and an abdominopelvic cavity (divided into the abdominal cavity and the pelvic cavity) separated by the diaphragm.
    3. Smaller cavities within the head include the oral cavity, nasal cavity, orbital cavities and middle ear cavities.